1. Field of the Invention
This invention relates to a shift mechanism for an automatic transmission having a brake pedal interlock. In particular the invention pertains to a shift mechanism mounted on the steering column of a motor vehicle.
2. Description of the Prior Art
U.S. Pat. No. 3,942,614 describes a safety interlock for a automatic transmission shift mechanism mounted on the vehicle steering column. In that device, the gear selector shaft extending parallel to the steering column is pivotally actuated by a manual selector lever and moves between park and drive position. The brake pedal for actuating the wheel brakes of the vehicle is moveable between an unactuated and an actuated position. When the brake pedal is not actuated in a locking position, a locking mechanism, in a form of a locking bolt actuated by a solenoid, is located where movement of the manual selector lever from the park position to the drive position is blocked. When the brake pedal is actuated, the solenoid is energized through a switch and an electrical connection, thereby moving the locking bolt to a position where the operation is free to select the operating range of the transmission by moving the gear selector mechanism to the selected position.
The gear shift mechanism described in the '614 patent has the disadvantage that the locking bolt is located transversely to the pivoting movement of the selector mechanism, which pivots due to the effect of manual selector lever and a gear shift shaft movement. Furthermore, a force applied by the operator of the motor vehicle to the manual selector lever transversely to the locking bolt is applied to the locking bolt. Consequently, the locking mechanism can be damaged easily or deformed as a result of an attempt to move the manual selector lever forcibly from the park position to the drive position. Damage to the mechanism resulting from this action impairs operation of the mechanism.